This invention relates generally to circuitry for energizing gaseous displays and more particularly to circuitry for energizing a bar graph display from a digital input.
In the bar graph display associated with the present invention, a series of linearly arranged cathode elements are sequentially energized by phased clocking circuitry. As long as a unitary anode element overlying the cathode elements is energized, sequential illumination occurs, forming a bar display. The height of the bar is then determined by properly de-energizing the overlying anode.
In the prior art, this de-energization of the anode electrode has been typically controlled by a voltage comparator circuit. The comparator is supplied with an analog voltage level representing bar height and with a ramp signal. When the ramp exceeds the analog level, the bar graph anode is de-energized. Using this analog approach, digital information must be converted to analog form in order to be displayed. Such techniques have proven burdensome and unduly expensive when it is desired to display digital output in a bar graph format.